Textbook 9C.5

[Nancy Li 1C]

Can someone explain how to go about this problem? I don't understand how to figure out how many places the ligand can bond to.
"Which of the following ligands can be polydentate? If the ligand can be polydentate, give the maximum number of places on the ligand that can bind simultaneously to a single metal center:
a) HN(CH2CH2NH2)2
b) CO3 2-
c) H2O
d) oxalate

[Anika Scott 3A]

First of all, I am pretty sure Lavelle has a chart of the polydentate on his website that might be helpful to refer to. Although in terms of this questions HN(CH2CH2NH2)2 is a Tridentate ligand because there are three nitrogen's in this structure that each have a lone pair. CO3 2- is a mono or bidentate Ligand because the CO3 can bind to either one or two oxygen atoms. H2O is a monodentate ligand because regardless of the two lone pairs on oxygen, the metal atom can only bind to one. And finally, oxalate is a bidentate ligand because there are two oxygens with a single bond and two oxygens with a double bond.